Multiple Choice
Which property is shared by all isotopes of calcium, and which property differs among them?
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2. Atoms & Elements
Isotopes
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Which isotope of lead has 126 neutrons?
A
Pb-208
B
Pb-207
C
Pb-204
D
Pb-206
Verified step by step guidance1
Recall that the number of neutrons in an isotope is given by the difference between the mass number (A) and the atomic number (Z) of the element: \(\text{Number of neutrons} = A - Z\).
Identify the atomic number (Z) of lead (Pb), which is 82. This means every lead atom has 82 protons.
For each isotope, subtract the atomic number from the mass number to find the number of neutrons: for example, for Pb-208, neutrons = \$208 - 82$.
Calculate the number of neutrons for each isotope: Pb-208, Pb-207, Pb-204, and Pb-206, and compare each result to 126 neutrons.
Select the isotope whose neutron count matches 126, which confirms the correct isotope with 126 neutrons.
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